1. Field of the Invention
The present invention relates to a tapered roller bearing.
2. Description of the Related Art
Heretofore, there has been known tapered roller bearings such as that shown in FIG. 6. The tapered roller bearing is provided with an inner ring 210, an outer ring 230, a plurality of tapered rollers 240, and a cage 250. The inner ring 210 has an outer peripheral surface formed as an inner ring raceway surface 213 in the shape of a tapered shaft. The outer ring 230 is disposed concentrically on the outer peripheral side of the inner ring 210 and has an inner peripheral surface formed as an outer ring raceway surface 231 in the shape of a tapered hole. The tapered rollers 240 are disposed to be rollable in an annular space between the inner ring raceway surface 213 and the outer ring raceway surface 231. The cage 250 has a plurality of pockets 251 in which the respective tapered rollers 240 are held.
There has been known tapered roller bearings, such as those disclosed in Japanese Patent No. 4975293 (JP 4975293 B) in which tapered roller bearings have cutouts that are provided in cage bars on the narrow width side of pockets in a cage and in the pocket center portions of a small annular portion so that the cutouts allow lubricating oil flowing between the cage and an inner ring to flow toward an outer ring side.
In the tapered roller bearing of the related art shown in FIG. 6, while the bearing is rotating, lubricating oil supplied toward a small-diameter side of the tapered roller bearing branches off to flow into a first flow path R1′ that extends into the tapered roller bearing through a clearance between an inner peripheral surface of a flange 254a formed in a small-diameter side annular portion 254 of the cage 250 and a small-diameter side outer peripheral surface of the inner ring 210, and a second flow path R2′ that extends along the outer surface of the flange 254a of the cage 250 and then extends toward a small-diameter side inner peripheral surface of the outer ring 230. While the bearing is rotating, the lubricating oil that has flown into the tapered roller bearing through the second flow path R2′ is subjected to the action of a centrifugal force and flows from a small-diameter side of the outer ring raceway surface 231 toward a large-diameter side of the outer ring raceway surface 231. Accordingly, the pressure in an inner region A′ is low which is defined by the inner peripheral surface of the outer ring 230 on the small-diameter side, a small end face 241 of each tapered roller 240 and an outer peripheral surface of the small-diameter side annular portion 254 of the cage 250. On the other hand, the lubricating oil flowing through the second flow path R2′ hits the small-diameter side inner peripheral surface of the outer ring 230 and thus, the pressure in an outer region B′ is high which is near the small-diameter side inner peripheral surface of the outer ring 230. Consequently, because the lubricating oil in the outer region B′ is drawn into the inner region A′, the amount of the lubricating oil flowing through the bearing is increased, and a torque loss due to flow resistance of the lubricating oil increases. In the tapered roller bearing disclosed in JP 4975293 B, the cutouts of the cage allow the lubricating oil flowing between the cage and the inner ring to flow toward the outer ring side. However, because the pressure in the inner region A′ is low and the lubricating oil in the outer region B′ is drawn into the inner region A′, it is unlikely that favorable effect is produced for decreasing the amount of the lubricating oil flowing through the bearing.